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Related Concept Videos

Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

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Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial...
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Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

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Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death.  Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
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Protein Import into the Peroxisomes01:27

Protein Import into the Peroxisomes

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Cells contain membrane-bound organelles called peroxisomes that oxidize organic molecules by transferring hydrogen atoms to oxygen, producing hydrogen peroxide. Peroxisomes enzymatically convert the released hydrogen peroxide into water and oxygen.
Peroxisomal Protein Import:
Peroxisomes lack the genetic machinery required to code for their own proteins. Hence, most peroxisomal membrane, lumenal and transmembrane proteins are synthesized in the cytoplasm or ER and transported to the peroxisome...
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Protein Transport to the Inner Chloroplast Membrane01:18

Protein Transport to the Inner Chloroplast Membrane

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Proteins targeted to the inner chloroplast membrane, or plastid proteins, are transported by two general pathways: the stop-transfer and the re-insertion or post-import pathways. Most plastid proteins carry N-terminal transit sequences and internal import sequences targeting it to the specific chloroplast subcompartment. Proteins targeted by the stop-transfer pathway have internal hydrophobic sequences that inhibit their translocation into the stroma. As a result, these precursors are arrested...
2.6K
Nuclear Localization Signals and Import01:46

Nuclear Localization Signals and Import

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Proteins targeted to the nucleus carry short stretches of amino acid sequences called the nuclear localization signal or NLS. Classical nuclear localization signals are of two types: monopartite and bipartite NLS. Monopartite classical NLS (cNLS) consists of a single cluster of 4-8 amino acids. Bipartite cNLS consists of two clusters of  2-3 amino acids and a 9-12 residue long proline-rich linker bridging the two clusters. Signal clusters are rich in positively charged amino acids such as...
8.5K
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

5.2K
Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
Transport of mitochondrial precursors across the TIM23 channel is driven by...
5.2K

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Targeted Next-generation Sequencing and Bioinformatics Pipeline to Evaluate Genetic Determinants of Constitutional Disease
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Unlocking the presequence import pathway.

Christian Schulz1, Alexander Schendzielorz1, Peter Rehling2

  • 1Institute of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany.

Trends in Cell Biology
|December 28, 2014
PubMed
Summary
This summary is machine-generated.

Mitochondrial protein import relies on the translocase of the outer membrane (TOM) and inner membrane (TIM23) complexes. Recent advances clarify how precursor proteins navigate the intermembrane space and are translocated into the mitochondrial matrix via the Hsp70 motor.

Keywords:
Hsp70PAMTIM23TOMmitochondriaprotein translocation

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Area of Science:

  • Mitochondrial biology
  • Protein translocation
  • Molecular mechanisms

Background:

  • Mitochondrial protein import is crucial for cellular function.
  • The translocase of the outer membrane (TOM) and presequence translocase of the inner membrane (TIM23) facilitate protein transport.
  • Precursor proteins require specific targeting signals for import.

Purpose of the Study:

  • To review recent advances in understanding mitochondrial protein transport.
  • To elucidate the mechanisms of the presequence pathway.
  • To highlight the roles of TOM, TIM23, and the Hsp70 motor.

Main Methods:

  • Review of recent literature on mitochondrial protein import.
  • Analysis of the molecular machinery involved in presequence pathway translocation.
  • Focus on the interplay between TOM, TIM23, and the Hsp70 motor.

Main Results:

  • The TOM complex mediates initial recognition and outer membrane transport.
  • Tim50 in the intermembrane space triggers TIM23 rearrangements for inner membrane translocation.
  • The Hsp70 motor drives unfolding and translocation into the mitochondrial matrix.

Conclusions:

  • The presequence pathway involves intricate coordination between outer and inner membrane translocases.
  • Dynamic remodeling of the Hsp70 motor is essential for efficient protein import.
  • Continued research is vital for a comprehensive understanding of mitochondrial protein biogenesis.